Temperature Trends in Iran during the Last Half Century

Iran is located in the mid latitude dry zone. The annual mean temperature of the country is about 18 degree Celsius. During the past 50 years, we have seen positive and negative trends in temperature time series in Iran. In order to evaluate the trends, monthly temperature records from (according nightly, daily and circadian temperatures) Jan 1951 to Dec 2000 were examined using about 414000 observations throughout Iran. Kriging interpolator was applied to this data-base, monthly isothermal map of the whole country with a resolution of 15*15 Km have been made. So each map consists of 7238 pixels. In order to detect the spatial pattern of temperature trends, time series of nightly, daily and circadian temperature over every pixel of the isothermal maps have been analyzed using least squares regressions.This trend analysis suggests that the annual mean temperature of Iran shows that during the last half century the nightly, daily and circadian Iran’s temperature has been increased respectively with a regularity about 3,1,2 degree Celsius per century. The increasing temperature trends are mainly seen in hot lowlands and decreasing temperature mainly in mountain ranges.